What Myasthenia Gravis Drugs are Safe During Pregnancy?

Pregnancy is an exciting time. But, for those with autoimmune conditions such as myasthenia gravis (MG), pregnancy may be accompanied by feelings of apprehension. People with MG respond to MG differently, meaning that there is no 1 characteristic response.¹ This unexpected outcome may contribute to those feelings of apprehension.

How does it impact MG?

For those who were diagnosed with MG prior to pregnancy, the effect of pregnancy on MG can be variable. Those who were stable and well-controlled prior to pregnancy will likely continue to be stable throughout pregnancy.² However, this is not representative of all people; some MG symptoms may worsen during pregnancy.²

On the other hand, women who were not stable prior to pregnancy may continue to experience flares during pregnancy, with the majority of these flares occurring in the first trimester and right after giving birth.²

To highlight this further, a study conducted with 225 women with MG showed the following:¹

• 30 percent of women had no change in their condition
• 29 percent of women showed improvement in symptoms
• 41 percent of women experienced flares or exacerbations of MG

The current recommendation is that women with MG plan their pregnancy with their healthcare team.² The reason for this recommendation is due to the potential high-risk natures of these pregnancies.

Drugs and MG

Not all drugs used in MG can safely be continued throughout pregnancy. Some of these drugs are actually harmful to the baby and need to be discontinued, such as methotrexate. Methotrexate can cause fetal abnormalities and even fetal death.³

Other drug considerations in pregnancy are outlined below. Please note that this list is not exhaustive - seek advice from your doctor if you have questions about the risks or benefits of your medication:^4-8

• Mycophenolate (Cellcept) should also not be used in pregnancy.
• Azathioprine (Imuran) is classified as pregnancy risk factor D, meaning that there is evidence of harm to the fetus, but the benefit of using the drug may outweigh the harms. Some adverse events of azathioprine use in pregnancy include low birth weight and high blood pressure in the mother. If you are on this drug and considering pregnancy, your doctor will outline the relevant risks for you to consider.
• Rituximab may cross the placenta and may cause unwanted outcomes for the baby.
• Pyridostigmine, while also crosses the placenta, is typically the drug of choice for pregnant women with MG .
• Corticosteroids, such as prednisone, are also generally considered acceptable to use in pregnancy, even though the drug crosses into the placenta.

What to expect post-pregnancy

Following pregnancy, management is also needed to ensure that medications continue to be safe if breastfeeding. For example, breastfeeding is not recommended while on methotrexate, cyclosporine, or azathioprine.⁹

Managing MG during pregnancy can be stressful and overwhelming. Fortunately, we have more evidence now to inform guidelines on how to manage MG during pregnancy. With the right healthcare team and planning, pregnancy can be safe for both the mother and the baby.

Did you have to change your MG medication after a positive pregnancy? Share your experiences below!